Great minds think alike… its unlikely that you read the Part 1 its a bit TL;DR; to be frank.
Assuming you have a Windows Universal project or are starting there and are also interested in targeting Windows 10. Here is me creating a blank Windows 8.1 Universal project using Blank template.
This is what Windows Universal Project looks like… You have the Windows head (that’s what they called it), the Windows Phone head and the Shared head.
Whatever is in the shared head is copied to Windows & WindowsPhone head as the first step of compiling the project. Its a neater version of sharing a file by adding a file reference (Add existing file > Add link).
All shared stuff goes in Shared head. Anything specific to either head goes in Windows or WindowsPhone heads. Shared head usually includes all the Models, ViewModels, Services, Helpers, Behaviours and whatever stuff you don’t what to put in PCL (not everyone uses PCLs)
Lets add Windows 10 project to the solution
We need a few minor adjustments before Windows 10 project becomes a part of Windows Universal and thinks the same way. Lets delete the App.xaml and App.xaml.cs to start with.
Next right click unload Windows head and then right click and choose Edit
Scroll all the way down until you see something like this
Copy this line.
Now unload and edit the Windows 10 project. Scroll to the bottom to the exact same spot and paste the line without any changes.
Save and close. Reload both Windows head and Windows 10 project and that’s it. The Windows 10 universal project is now a part of Windows Universal project. The circle is complete.
All items in shared head are now a part of Windows 10 head and all you need to do is add Windows 10 head specific bits like you have for Windows 8.1 and Windows Phone 8.1
You build for store like you build before.
You have appx / appxbundle for
Windows (x86 / x64 / ARM)
Windows 10 (x86 / x64 / ARM) compiled to Native